MRI guided muscle biopsy confirmed polymyositis diagnosis in a patient with interstitial lung disease

Idiopathic inflammatory myopathies, such as polymyositis (PIM), may present with general symptoms such as fever and fatigue and only minimal muscle we akness, making it difficult to make a definite diagnosis and provide adequa te treatment. Here a case is described in which interstitial lung disease w as the first and most prominent manifestation of PM. Later, when muscle wea kness became apparent and inflammatory muscle disease was suspected the fir st muscle biopsy was non-diagnostic. However, magnetic resonance imaging (M RI) scans of the clinically weak thigh muscles showed high signal on T-2 we ighted images, suggesting muscle inflammation more proximal to the first bi opsy site. A second biopsy at this site disclosed typical histopathological findings for myositis. After treatment with prednisolone in combination wi th cyclophosphamide both pulmonary and muscle function improved. Conclusion-MRI scans of muscles may be helpful in selection of a site for m uscle biopsy in patients with suspected inflammatory myopathy when a first muscle biopsy turns out to be negative. Additionally, patients with interst itial lung disease of unknown cause should be tested for muscular function to exclude an associated inflammatory muscle disorder.